U.S. Pat. No. 6,615,799 B2 (JP-A-2002-310039) discloses a fuel injection pump including a camshaft, a cam, a sliding member, and a plunger. The cam is eccentric with respect to the camshaft. The sliding member is slidable and rotatable with respect to the outer circumferential periphery of the cam. The plunger is configured to pressurize and feed fuel in a compression chamber.
The cam is eccentric with respect to the center axis of the camshaft and rotatable integrally with the camshaft. The sliding member revolves around the center axis of the camshaft in conjunction with rotation of the camshaft. The plunger as a sliding member is slidable and configured to convert revolution of the sliding member into a reciprocal movement. In the present structure, the plunger conducts the reciprocal movement so as to pressurize and feed fuel in the fuel compression chamber.
More specifically, U.S. Pat. No. 6,615,799 B2 discloses a three-cylinder fuel injection pump including a housing, which has three cylinders and three fuel compression chambers, and three plungers each slidable in each cylinder and configured to pressurize and feed fuel drawn into the fuel compression chamber. The sliding member is in a ring shape and entirely surrounds the outer circumferential periphery of the cam. The sliding member is in a hexagonal shape having straight and arc-shaped outlines. The three plungers are located at intervals of 120 degrees, and having a straight outline slidably in contact with the sliding member. In the present structure, the sliding member has three sliding surfaces located at intervals of 120 degrees. The three plungers alternately pump fuel in the three compression chambers in conjunction with rotation of the camshaft. According to U.S. Pat. No. 6,615,799 B2, the outer circumferential periphery of the cam has a groove to lead lubricate oil into a sliding portion between the outer circumferential periphery of the cam and the sliding member.
In recent years, increase in discharge pressure of a fuel injection pump is demanded. When the discharge pressure is increased, surface pressure applied to the sliding portion between the cam and the sliding member becomes high. Therefore, supply of sufficient fuel is required to the sliding portion. However, in the structure of U.S. Pat. No. 6,615,799 B2, the sliding member is in a ring shape and entirely surrounds the outer circumferential periphery of the cam. Accordingly, it is hard to supply sufficient fuel to the sliding portion.